Upper bearing assemblies in current use for support of navigational radar antenna masts, have various problems associated therewith, primarily attributable to grease fittings that are not readily visible and are inaccessible after bearing installation on a submarine, for example, leading to improper lubrication and excessive bearing wear requiring frequent replacement of such bearing assemblies. Bearing replacement involving removal of the antenna mast is a labor intensive task, especially in view of the weight of bearing parts. It is therefore an important object of the present invention to provide a bearing assembly for the foregoing type of installation which is more easily installed and replaced with reduced weight parts and which is less likely to experience and/or impose rapid or excessive wear.